摘要:

Until now, little attention has been paid to load-flow methods with variables expressed in rectangular form. These methods could have some advantages over existing methods in polar form, bearing in mind the large amount of computation required for load-flow calculations in large networks where evaluation of polar trigonometric functions is necessary. This paper presents several decoupled load-flow methods, some of them having very good convergence and time characteristics, based on the application of Newton's method to equations of nodal power or current mismatches with the variables, i.e. the nodal voltages, expressed in rectangular form. All the methods presented are compared with several variants of the decoupled load-flow method with variables in polar form. The methods given are applied in studies of electrical networks with different voltage levels from distribution to EHV and various elements, including transformers, cables, short lines, long lines, as well as conditioned and ill-conditioned systems. Comparison is made between all methods by noting the number of iterations for converged solutions from a common start to the end of the iteration process.

DOI:10.1049/ip-c.1983.0018

出版商:IEE    

年代:1983

数据来源: IET

摘要:

One of the basic approaches to the static state estimation of power systems involves the solution of the so-called independent equations using conventional load-flow techniques, such as Newton-Raphson (NR) and fast decoupled (FD). Of these two, the FD method is preferred to the NR approach, primarily because of reduced computational requirements. As is well known, the superiority of the former is primarily attributable to the underlying ‘decoupling’ assumptions, among others. However, since these assumptions are not valid for all modes of system operation, the results provided by the FD estimator may be unreliable. Moreover, as the computational requirements of the NR estimator are prohibitively large and the results obtained from the FD method might be suspect, especially in the real-time environment, this paper presents a new steady-state estimator, combining all the attractive features of both the NR and FD methods, while remaining free from their limitations. The new estimator is based on a complete Taylor's series expansion of nodal and line-flow equations in Cartesian co-ordinates. The capability of the proposed method to serve as a real-time monitor is demonstrated by digital simulation studies on a number of sample power systems, the results being compared with those of the FD method. This comparison reveals that, owing to its exact formulation, lower computational requirements, and the ability to provide a reliable system state even during unusual operating conditions, the proposed method is a practically viable and preferred analytical tool for real-time monitoring of power systems.

DOI:10.1049/ip-c.1983.0019

出版商:IEE    

年代:1983

数据来源: IET

摘要:

The recently developed high-frequency link or power-system intertie incorporates two naturally commutated cycloconvertors (NCCs) with a high-frequency passive resonating tank circuit. A new circuit configuration of thy ristors for the NCC has been developed which achieves improved operating characteristics compared to the conventional NCC. The theoretical and practical results of the new NCC show improved output voltage distortion and reduced input reactive loading compared to the standard NCC, both of which are advantageous when used in high-frequency links. Implementation of the new NCC is discussed together with a critical comparison between the two types.

DOI:10.1049/ip-c.1983.0020

出版商:IEE    

年代:1983

数据来源: IET

摘要:

Large convertors such as DC drives or HVDC schemes will generate noncharacteristic harmonics if fed from unbalanced AC busbars. In particular, high levels of third harmonic may be generated. The paper describes the mechanism for the generation of this third harmonic both for conventional and equally pulse spaced (phase locked) control systems. The mechanisms are shown to be different. It is also shown that noninfinite reactances on the DC side of the convertors can increase the harmonics, in particular if there is a second-harmonic series resonance between the DC reactors and the cable or line capacitance.

DOI:10.1049/ip-c.1983.0021

出版商:IEE    

年代:1983

数据来源: IET

摘要:

The paper outlines a new method of distance protection that has been developed to provide true ultra-high-speed tripping for transmission line faults in both 50 Hz and 60 Hz systems. Techniques are described for deriving and comparing signals that are specially developed finite Fourier transforms, which are particularly well suited to real-time implementation using finite impulse response transversal filter functions. A particularly economical hybrid realisation using charge-coupled devices and a 16-bit microprocessor is described, and methods for retaining directional stability and dynamic accuracy are given. The paper concludes with a presentation of the results of studies to determine the performance of the new relays when used in conjunction with a conventional capacitor voltage transformer.

DOI:10.1049/ip-c.1983.0022

出版商:IEE    

年代:1983

数据来源: IET

摘要:

The application of the inverse definite minimum time (IDMT) overcurrent relay to power system protection is reviewed, and the present methods for determining its settings are briefly described. A computer program to calculate relay settings based on a generalised procedure, and therefore suitable for both radial and interconnected ring systems, is then proposed. Its application to a specific interconnected system is explained. Two further programs have been developed to be used in conjunction with the first one. These assess, by a simulated circuit breaker tripping facility, how the IDMT protection would perform on an interconnected ring power system when there occurs either a failure of the main protection or a circuit breaker on the faulted section.

DOI:10.1049/ip-c.1983.0023

出版商:IEE    

年代:1983

数据来源: IET

DOI:10.1049/ip-c.1983.0024

出版商:IEE    

年代:1983

数据来源: IET